Method of making coaxial electric cables



June 13, 1967 J. MAESLONA ETAL 3,325,321

METHOD OF MAKING COAXIAL ELECTRIC CABLES Filed Feb. 13. 1964 2Sheets-Sheet 1 Inventors JAN MASOA/A GERALD ILMOREL ory J. MASLONA ETALMETHOD OF MAKING COAXIAL ELECTRIC CABLES June 13, 1967 2 Sheets-Sheet 2Filed Feb. 15. 1964 AL R OR LO T 0 m w MM A w MM w United States Patent3,325,321 METHOD OF MAKING COAXIAL ELECTRIC CABLES Jan Maslona andGerald Alan Morel, London, England,

assignors to International Standard Electric Corporation, New York,N.Y., a corporation of Delaware Filed Feb. 13, 1964, Ser No. 344,632Claims priority, application Great Britain, Mar. 1, 1963, 8,316/63 3Claims. (Cl. 156-54) This invention relates to coaxial electric cables.

According to the present invention there is provided a coaxial cablewhich includes an inner conductor, an outer conductor and electricalinsulating material supporting the inner conductor and bonded to theouter conductor.

Further according to the present invention there is provided a method ofmanufacturing a coaxial cable which includes the steps of placingelectrical insulation around an inner conductor, placing an outerconductor round the insulation and bonding the electrical insulation tothe outer conductor.

In the accompanying drawings which illustrate embodiments of the presentinvention.

FIG. 1 is a perspective view of a coaxial cable with a portion of theouter conductor removed,

FIG. 2 is a similar perspective view to that shown in FIG. 1, but of adifferent coaxial cable,

FIG. 3 is a perspective view of a metal strip, with pieces ofinsulation, disposed thereon, and

FIG. 4 is a perspective view of a coaxial cable having the metal stripin FIG. 3 applied as an outer conductor, and

FIG. 5 is a perspective view of another metal strip, with pieces ofinsulation.

Referring to FIG. 1, there is shown an inner conductor 1, cellularpolythene insulating cylinders 2, and an outer conductor 3. Theinsulating cylinders 2 have a radial slit 4 and on the inner surface ofthe outer conductor 3 there is a polythene coating 5 which is bonded tothe insulating cylinders 2.

The coaxial cable is manufactured by extruding cellular polytheneinsulating material in a continuous length of cylinderical shape,cuttingit into the cylinders 2, and then cutting the slits 4 in thecylinders 2. The cylinders 2 are then placed on the inner conductor 1 atspaced intervals along its length by pressing the inner conductor 1 inthe slots 4. The outer conductor 3 in the form of a polythene coatedmetal strip is longitudinally folded round the cylinders 2 with thepolythene coating 5 on the inside. The outer conductor 3 is then heatedto weld the cylinders 2 to the polythene coating 5.

If desired the cylinders 2 may be replaced by continuous solid orcellular polythene insulation which is extruded directly about the innerconductor 1. The outer conductor 3 may be formed by helically windingone or more polythene coated tapes round the cylinders 2.

In the embodiment shown in FIG. 2 like parts are designated with thesame reference numerals as those in FIG. 1. The inner conductor 1 hasspaced discs 6 of polythene on it instead of the cylinders 2 of cellularpolythene. In the discs 6 there is a radial slit 7.

This alternative construction of coaxial cable is manufactured in asimilar manner to the coaxial cable shown in FIG. 1, with the discs 7bonded to the coating 5.

Referring to FIGS. 3 and 4 there is shown a metal strip 8 having apolythene coating 9 and pads 10 of cellular polythene bonded to thepolythene coating 9. In FIG. 4 the metal strip 8 together with the pads10 is shown being folded round an inner conductor 11. This forms aconstruction with an outer conductor 12 separated from the innerconductor 11 by the pads 10 which are bent to form cylinders round theinner conductor 11.

The pads 10 are cut from a strip of extruded cellular polythene andplaced on the polythene coating 9. The assembly is then heated to bondthe polythene coating 9 to the pads 10.

If desired strips of polythene may replace the pads 10 of cellularpolythene. These polythene strips may cross the metal strip at rightangles and so form discs round the inner conductor 11 when the metalstrip 8 is folded round it. As shown in FIG. 5, the polythene strips 13also may cross the metal strip 8 diagonally in such a manner that theyprovide a continuous helix round the inner conductor 11 with the ends ofdifferent strips in contact. With reference to FIGURE 5, ends A and Bwould interface, and ends C and D as well, forming a helical insulationabout conduct-or 11 when metal strip 8 is folded.

In the embodiments described the outer conductor is bonded to theinsulating material supporting the inner conductor by means of heatingwhich causes fusion to take place between the insulating material and alayer of similar material on the inner surface of the outer conductor.

'It is not essential for the two materials to be similar so long as theyare capable of fusing together, and the layer of material need not becontinuous between the pieces of supporting insulating material.

The supporting material need not be bonded to the outer conductorthrough the intermediary of a similar material. An adhesive layer may beapplied directly to the inner surface of the outer conductor, and thesupporting material may be bonded by means of this layer to the outerconductor. It is possible for the adhesive layer to be applied to thesupporting material.

It is to be understood that the foregoing description of specificexamples of this invention is not to be considered as a limitation onits scope.

What we claim is:

1. A method of manufacturing a coaxial cable comprising the steps of:

bonding longitudinally spaced quadrangular pieces of thermoplasticinsulating material to a longitudinal metal strip; and

longitudinally folding said metal strip about an inner conductor so thatsaid pieces of insulating material encircle and support said innerconductor.

2. A method as claimed in claim 1 in which the spaced pieces formcylinders at spaced intervals along the length of the inner conductorwhen applied thereto.

3. A method as claimed in claim 1 in which the spaced pieces form atleast one continuous helix round the inner conductor when appliedthereto.

(References on following page) 3 7 '4 References Cited 3,173,990 3/1965Lamons 174102 et a1. 31322 g et FOREIGN PATENTS 0e 1 1/1942 Scheldorf174 2s X 5 12/1950 Fmland' 11/1948 Gordon 584,153 1/1947 Great Bntam.

8/1957 Kinghorn 156-54 10/1957 Peters 174 1O2 EARL M. BERGERT, PrimaryExaminer.

2/1964 Mildner 174 2. JOHN F. BURNS, Examiner. 8/ 1964 'Hahne 174102 XD. A. KETTLESTRINGS, Assistant Examiner.

1. A METHOD OF MANUFACTURING A COAXIAL CABLE COMPRISING THE STEPS OF:BONDING LONGITUDINALLY SPACED QUADRANGULAR PIECES OF THERMOPLASTICINSULATING MATERIAL TO A LONGITUDINAL METAL STRIP; AND LONGITUDINALLYFOLDING SAID METAL STRIP ABOUT AN INNER CONDUCTOR SO THAT SAID PIECES OFINSULATING MATERIAL ENCIRCLE AND SUPPORT SAID INNER CONDUCTOR.